/*
 * Copyright (C) 2010 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.base;

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.caliper.Param;
import com.google.caliper.runner.CaliperMain;
import java.util.BitSet;
import java.util.Random;

/**
 * Benchmark for the {@link CharMatcher#whitespace} implementation.
 */
public class WhitespaceMatcherBenchmark {
    private static final int STRING_LENGTH = 10000;

    private static final String OLD_WHITESPACE_TABLE = "\u0001\u0000\u00a0\u0000\u0000\u0000\u0000\u0000"
            + "\u0000\u0009\n\u000b\u000c\r\u0000\u0000\u2028\u2029\u0000\u0000\u0000\u0000\u0000\u202f"
            + "\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0020\u0000\u0000\u0000\u0000\u0000"
            + "\u0000\u0000\u0000\u0000\u0000\u3000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000"
            + "\u0000\u0000\u0085\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a"
            + "\u0000\u0000\u0000\u0000\u0000\u205f\u1680\u0000\u0000\u180e\u0000\u0000\u0000";

    public static final CharMatcher OLD_WHITESPACE = new CharMatcher() {
        @Override
        public boolean matches(char c) {
            return OLD_WHITESPACE_TABLE.charAt(c % 79) == c;
        }
    };

    @Param
    private boolean useNew;

    @Param({"20", "50", "80"})
    private int percentMatching;

    private String teststring;
    private CharMatcher matcher;

    public static void main(String[] args) throws Exception {
        CaliperMain.main(WhitespaceMatcherBenchmark.class, new String[] {});
    }

    @BeforeExperiment
    protected void setUp() {
        BitSet bitSet = new BitSet();
        for (int i = 0; i < OLD_WHITESPACE_TABLE.length(); i++) {
            bitSet.set(OLD_WHITESPACE_TABLE.charAt(i));
        }
        bitSet.clear(0);
        bitSet.clear(1);
        matcher = useNew ? CharMatcher.whitespace() : OLD_WHITESPACE;
        teststring = newTestString(new Random(1), bitSet, percentMatching);
    }

    @Benchmark
    public int countIn(int reps) {
        int result = 0;
        CharMatcher matcher = this.matcher;
        String teststring = this.teststring;
        for (int i = 0; i < reps; i++) {
            result += matcher.countIn(teststring);
        }
        return result;
    }

    @Benchmark
    public int collapseFrom(int reps) {
        int result = 0;
        CharMatcher matcher = this.matcher;
        String teststring = this.teststring;
        for (int i = 0; i < reps; i++) {
            result += System.identityHashCode(matcher.collapseFrom(teststring, ' '));
        }
        return result;
    }

    private static String allMatchingChars(BitSet bitSet) {
        final char[] result = new char[bitSet.cardinality()];
        for (int j = 0, c = bitSet.nextSetBit(0); j < result.length; ++j) {
            result[j] = (char) c;
            c = bitSet.nextSetBit(c + 1);
        }
        return new String(result);
    }

    private static String newTestString(Random random, BitSet bitSet, int percentMatching) {
        final String allMatchingChars = allMatchingChars(bitSet);
        final char[] result = new char[STRING_LENGTH];
        // Fill with matching chars.
        for (int i = 0; i < result.length; i++) {
            result[i] = allMatchingChars.charAt(random.nextInt(allMatchingChars.length()));
        }
        // Replace some of chars by non-matching.
        int remaining = (int) ((100 - percentMatching) * result.length / 100.0 + 0.5);
        while (remaining > 0) {
            final char c = (char) random.nextInt();
            if (bitSet.get(c)) {
                final int pos = random.nextInt(result.length);
                if (bitSet.get(result[pos])) {
                    result[pos] = c;
                    remaining--;
                }
            }
        }
        return new String(result);
    }
}
